This invention relates to an organic EL (electro-luminescence) display forming light-emitting layers capable of making a full color display, and to a device for production of a color filter.
An organic EL element is an element constituted of a thin film containing a fluorescent organic compound, said film being held between a cathode and an anode. When an electron and a hole are injected into the thin film and recombined, an exciton is formed, and upon de-activation of the exciton, a light (fluorescent light or phosphorescent light) is emitted from the element.
Characteristic feature of the organic EL element consists in that it can emit a surface light having so high luminance as 100 to 100,000 cd/m2 at a low voltage of 10 V or less, and it can emit a light ranging from blue color to red color by selecting the kind of fluorescent material.
In WO 99/48339, there is disclosed a technique of forming a full color display type organic EL display by subjecting an organic EL material which has so far been considered impossible to pattern to an ink jet process (the piezo jet process and the process of discharging the material by the action of thermally caused bubble formation).
However, the above-mentioned WO 99/48339 makes no mention about the means for letting fly an organic EL material against fine pixels and the method for improving the reliability by giving a flying drop shape necessary for forming a uniform organic light emitting layer and preventing the clogging of ink jet nozzle.
For letting an organic EL material fly by the ink jet process, it is necessary to dissolve the organic EL material in a solvent to form a dilute solution so that the drops can fly.
Further, for vaporizing off the solvent after flying of the solution and thereby forming an organic light-emitting layer, it is also necessary that the solvent used has a high volatility.
However, in the hitherto adopted piezo driving ink jet process or the discharging process by the thermally caused bubble formation, the nozzle has to have a small diameter at the ink jet head in order to make small the flying quantity of organic EL material solution so as to match with the fineness of pixel. As its result, a solvent of high volatility dries up at the tip of nozzle to cause clogging of the nozzle.
Further, it has been difficult in the ink jet process (the piezo jet process and the discharging process by thermally caused bubble formation) to form a uniform organic light-emitting layer because, in the ink jet process, the solution of organic EL material flies in the form of fine dots and a pixel is formed as an assembly of the dots.
This invention aims at solving the problems mentioned above, and the object thereof is to provide a production device of organic EL display capable of making a full color display by patterning red-, green- and blue-colored uniform organic light emitting layers at every pixel in a high reliability by the action of an electrostatic field. A further object of this invention is to provide an organic EL display which is uniform and free from color mixing, by the use of said production device.
According to one embodiment of the present invention, the device for producing an organic EL display of this invention has a means for storing a solution in which a light emitting material is dissolved, a means for feeding the solution to a tip of a flying electrode, a means for applying a voltage between the tip of the flying electrode and an electrically conductive material of an organic EL substrate and thereby forming an electrostatic field, and a means for relatively shifting the tip of the flying electrode and the organic EL substrate to a perpendicular direction and to a horizontal direction, and is so constructed that the solution is formed into the form of a stringy beam from the tip of the flying electrode to let it fly onto the organic EL substrate, thereby injecting the solution into a concavity formed and surrounded by banks on the organic EL substrate, and forming red, green and blue light emitting layers.
Additionally, a thickness of the stringy beam of the solution can be varied by controlling the electrostatic field.
Meanwhile, the stringy beam referred to herein shows a state that a solution outgone from a tip of 3-1 of the flying electrode, for example at shown at FIG. 1, is reaching the organic EL display 1 at successive state at least at one point, and the stringy beam is different from an ink in the form of dots emitted in the case of the ink jet process for printing characters etc.
Further, the amount of injection of the solution can be varied by controlling a velocity of relatively shifting the tip of the flying electrode and the organic EL substrate to a perpendicular direction.
Further, said means for forming an electrostatic field can be formed by applying a voltage obtained by in-series overlapping a pulse voltage on a direct current voltage of bias and said stringy beam can be intermittently cut by controlling the electrostatic field.
Further, said solution can be injected into a concavity formed and surrounded by the bank and, after vaporizing off the solvent, the injection of the solution can be repeated additionally.
Further, said device can have a plurality of the flying electrodes.
According to another embodiment of the present invention, the device for producing a color filter of the present invention has a means for storing a solution in which a light transmitting material is dissolved, a means for feeding said solution to a tip of a flying electrode, a means for applying a voltage between the tip of a flying electrode and an electro-conductive material of a color filter substrate and thereby forming an electrostatic field, and a means for relatively shifting the tip of the flying electrode and the color filter substrate to a perpendicular direction and to a horizontal direction, wherein said solution is formed into the form of a stringy beam to let it fly onto the color filter substrate, thereby injecting the solution into a concavity formed and surrounded by a black matrix on the color filter substrate, and forming red, green and blue light transmitting layers.
According to another embodiment of the present invention, the organic EL display of the present invention has a bank for partitioning pixels, wherein the partitioning by the bank exists only between pixels of different colors.
Further, according to another embodiment of the present invention, the organic EL display of the present invention has on a substrate a display portion composed of a plurality of pixels, wherein an electrode corresponding to each of the pixels is arranged to the plurality of pixels, and wherein, on the electrode corresponding to each of the pixels on the substrate, a light emitting layer of same color is arranged in the same layer over the plurality of pixels.
Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.